Title: "Ion-Engineered CVD Diamond Surfaces: Tribological Adaptation for Multi-Environment Self-Lubrication in Vacuum, Nitrogen, and Ambient Air" Abstract: This study investigates the enhanced tribological functionality of chemically vapor-deposited (CVD) diamond films subjected to targeted ion implantation as a surface-engineering innovation within lab-grown diamond technology. By comparing as-deposited fine-grain and polished coarse-grain CVD films with their carbon- and nitrogen-ion-implanted counterparts, the research demonstrates how ion modification enables retention of ultralow friction coefficients (<0.1) and wear rates (≤10⁻⁶ mm³/N·m) across three distinct operational environments: humid air, dry nitrogen, and ultrahigh vacuum (10⁻⁷ Pa). Unmodified CVD films exhibited significant performance degradation in vacuum, whereas ion-implanted films maintained consistent self-lubricating properties, attributed to the formation of a conductive, amorphous carbon surface layer that inhibits adhesive wear. These findings present a scalable, post-deposition treatment strategy for advancing CVD diamond applications in extreme-condition tribological systems where conventional diamond coatings fail.